1. Field of the Invention
The present invention relates to a realistic robot having a structure which emulates the mechanisms and movements of an organism, and, more particularly, to a leg-movement-type robot having a structure which emulates the body mechanisms and movements of, for example, a human being or a monkey, which walks while it is in an erect posture.
Even more specifically, the present invention relates to a leg-movement-type robot which walks on two feet while it is in an erect posture and which includes what one calls the upper half of the body, including the trunk, the head, the arms, and the like, provided on the legs. Still more specifically, the present invention relates to a robot which can move naturally in a way close to that of a human being and in a way sufficiently indicative of emotions and feelings with considerable fewer degrees of freedom than the actual mechanism of, for example, the human body.
2. Description of the Related Art
A robot is a mechanical device which emulates the movement of a human being by making use of electrical and magnetic actions. The term robot is said to be derived from the Slavic word ROBOTA (slavish machine). In our country, the use of robots began from the end of the 1960s, most of which were industrial robots, such as manipulators and conveyance robots, used, for example, for the purpose of achieving automatic industrial operations in factories without humans in attendance.
In recent years, progress has been made in the research and development of leg-movement-type robots which emulate the movements and mechanisms of the body of an animal, such as a human being or a monkey, which walks on two feet while it is in an erect posture. Therefore, there has been greater-expectation for putting such leg-movement-type robots into practical use. A superior feature of leg-movement-type robots which move on two feet while they are in an erect posture is that they can walk flexibly, for example, up and down steps or over obstacles.
In the history of leg-movement-type robots, research regarding leg movement was started by studying as elemental technology leg movement using only the lower limbs. Accordingly, robots of this type are not provided with all parts of the body which are positioned vertically.
For example, Japanese Unexamined Patent Publication No. 3-184782 discloses a joint structure applied to the structural part below the trunk of a robot which walks using the legs.
Japanese Unexamined Patent Publication No. 5-305579 discloses a controller for controlling the walking of a leg-movement-type robot. The controller disclosed in this document controls the walking of the robot so that the ZMP (zero moment point) matches a target value. The ZMP is the point on the floor surface where the moment resulting from the floor reaction force when the robot walks is zero. However, as can be seen from FIG. 1 in this document, a trunk 24 on which the moment acts is formed using a black box, so that not all parts of the body are provided. Therefore, the document is confined to proposing leg movement as elemental technology.
It goes without saying that the ultimate purpose of constructing leg-movement-type robots is to provide these robots with all parts of the body. More specifically, the ultimate purpose is to provide these robots which walk while they are in an erect posture on two feet with the lower limbs used for walking on two feet, the head, the upper limbs (including the arms), and the trunk which connects the upper and lower limbs. In such robots provided with all parts of the body, it is presupposed that work is carried out by moving the two legs while the robots are in an erect posture. In all cases where such work is carried out in the living space of human beings, it is necessary to control the robots so that the upper and lower limbs and the trunk move harmoniously in a predetermined order of priority.
Leg-movement-type robots which emulate the mechanisms and movements of human beings are called humanoid robots. Humanoid robots can, for example, help people in life, that is, help them in various human activities in living environments and in various circumstances in everyday life.
As is conventionally the case, leg-movement-type robots are roughly divided into those for industrial purposes and those for entertainment.
Industrial robots are intended to carry out various difficult operations, such as in industrial tasks or production work, in place of human beings. For example, they carry out in place of human beings maintenance work at nuclear power plants, thermal power plants, or petrochemical plants, or dangerous/difficult work in production plants or tall buildings. The most important theme is to design and manufacture industrial robots so that they can be industrially used as specified and can provide the specified functions. Industrial robots are constructed on the assumption that they walk on two feet. However, as mechanical devices, they do not necessarily have to faithfully reproduce the actual body mechanisms and movements of animals, such as human beings or monkeys, which walk while they are in an erect posture. For example, the freedom of movement of particular parts (such as the finger tips), and their operational functions are increased and enhanced, respectively, in order to produce an industrial robot for a particular use. On the other hand, the freedom of movement of parts considered comparatively unrelated to the use of the industrial robot (such as the head and arms) is limited or such parts are not formed. This causes the industrial robot to have an unnatural external appearance when it works and moves, although it is a type of robot which walks on two feet. However, for convenience in designing such a robot, such a compromise is inevitable.
In contrast, leg-movement-type robots for entertainment provide-properties closely connected to life itself, rather than help people in life such as by doing difficult work in place of human beings. In other words, the ultimate purpose of producing robots for entertainment is to make these robots faithfully reproduce the actual mechanisms of, for example, human beings or monkeys, which walk on two feet while they are in an erect posture, and to make them move naturally and smoothly. Since entertainment robots are structured to emulate highly intelligent animals, such as human being or monkeys, which stand in an upright posture, it is desirable that they move in a way sufficiently indicative of emotions and feelings. In this sense, entertainment robots which emulate the movements of human beings are rightly called humanoid robots.
In short, it is no exaggeration to say that entertainment robots, though intently called a leg-movement-type robot, shares the elemental technologies of industrial robots, but are produced for a completely different ultimate purpose and uses completely different hardware mechanisms and operation controlling methods to achieve the ultimate purpose.
As is already well known in the related art, the human body has a few hundred joints, so that it has a few hundred degrees of freedom. In order to make the movements of leg-movement-type robots as close to those of human beings, it is preferable that the leg-movement-type robots be allowed to move virtually as freely as human beings. However, this is technologically very difficult to achieve. This is because, since one actuator needs to be disposed to provide one degree of freedom, a few hundred actuators needs to be disposed for a few hundred degrees of freedom, thereby increasing production costs and making it virtually impossible to design them in terms of, for example, their weight and size. In addition, when the number of degrees of freedom is large, the number of calculations required for, for example, positional/operational control or balance control is correspondingly increased exponentially.
Restating what has been stated in another way, humanoid robots must emulate the mechanisms of the human body equipped with a limited number of degrees of freedom. Entertainment robots are required to move naturally in a way close to that of human beings and in a way sufficiently indicative of emotions and feelings with considerable fewer degrees of freedom than the human body.
Leg-movement-type robots which walk on two feet while they are in an erect posture are excellent robots in that they can walk flexibly (such as up and down steps or over obstacles). However, since the center of gravity of such robots is located at a high position, it becomes correspondingly difficult to perform posture control and stable walking control. In particular, the walking and the posture of entertainment robots need to be controlled while they move naturally and in a way sufficiently indicative of emotions and feelings like intelligent animals, such as human beings or monkeys.
Various proposals regarding the stable walking of leg-movement-type robots have already been made. For example, Japanese Unexamined Patent Publication No. 5-305579 discloses a leg-movement-type robot which is made to walk stably by matching with a target value the zero moment point (ZMP), that is, the point on the floor surface where the moment resulting from the reaction force of the floor when the robot walks is zero.
Japanese Unexamined Patent Publication No. 5-305581 discloses a leg-movement-type robot constructed so that the ZMP is either situated in the inside of a supporting polyhedral (polygonal) member or at a location sufficiently separated by at least a predetermined amount from an end of the supporting polyhedral (polygonal) member when a foot of the robot lands on or separates from the floor. As a result, even when the robot is subjected to an external disturbance, it is not affected thereby in correspondence with a predetermined distance, making it possible make the robot walk more stably.
Japanese Unexamined Patent Publication No. 5-305583 discloses the controlling of the walking speed of a leg-movement-type robot by a ZMP target location. More specifically, in the leg-movement-type robot disclosed in this document, previously set walking pattern data is used to drive an arm joint so that the ZMP matches a target location, and the tilting of the upper part of the body is detected in order to change the ejection speed of the set walking pattern data set in accordance with the detected value. Thus, when the robot unexpectedly steps on an uneven surface and, for example, tilts forward, the original posture of the robot can be recovered by increasing the ejection speed. In addition, since the ZMP can be controlled so as to match the target location, there is no problem in changing the ejection speed in a device for supporting both arms.
Japanese Unexamined Patent Publication No. 5-305585 discloses the controlling of the landing position of a leg-movement-type robot by a ZMP target location. More specifically, the leg-movement-type robot disclosed in this document is made to walk stably by detecting any shifts between the ZMP target location and the actually measured position and driving one or both arms so as to cancel the shift, or by detecting the moment around the ZMP target location and driving an arm so that it becomes zero.
Japanese Unexamined Patent Publication No. 5-305586 discloses the controlling of the tilting of the posture of a leg-movement-type robot by a ZMP target location. More specifically, the leg-movement-type robot disclosed in this document is made to walk stably by detecting the moment around the ZMP target location and driving an arm so that, when the moment is produced, the moment is zero.
However, none of the above-described proposals mention anything about controlling the posture and walking of the robot while it is moving naturally and in a way sufficiently indicative of emotions and feelings like intelligent animals, such as human beings or monkeys.
A robot called WABIAN (Waseda Bipedal Humanoid) is disclosed in a treatise called The Development of Humanoid Robots Which Walk On Two Feet (Third Robotics Symposia, May 7 and 8, 1998) by Yamaguchi et al. WABIAN is a complete humanoid robot which is provided not only with the lower limbs, but also with the upper limbs and the trunk, so that it is provided with all parts of the body. WABIAN has been developed for the purpose of producing a robot whose whole body moves harmoniously while it is walking. FIGS. 13 and 14 are each schematic views of an assembled structure of WABIAN. WABIAN has been designed and manufactured to overcome the problems involved in working while moving the whole body harmoniously. By controlling the ZMP and the yaw axis moment on the ZMP as a result of trunk or trunk/waist harmonious movement three axial moment compensation operations, the robot may be made to walk while its lower limbs, finger tips, and trunk take any path of movement. The mechanical models illustrated in the figures use extra super Duralumin as main structural material, and has a total weight of 107 kg and an overall length of 1.66 m when they are standing still in an erect posture.
Accordingly, it is an object of the present invention to provide an excellent robot having a structure which emulates the mechanisms and movements of the human body.
It is another object of the present invention to provide an excellent leg-movement-type robot which walks on two feet and which includes the upper half of the body, such as the trunk, the head, the arms, etc., formed on top of the legs.
It is still another object of the present invention to provide an excellent robot which can move naturally in a way close to that of a human being and sufficiently indicative of emotion and feelings with a considerable fewer degrees of freedom than a human being.
It is still another object of the present invention to provide an excellent robot in which the posture and the walking thereof can be controlled while the robot moves naturally and in a way sufficiently indicative of emotions and feelings like intelligent beings such as human beings or monkeys.
To these ends, according to a first aspect of the present invention, there is provided a leg-movement-type robot which moves using lower limbs. The robot comprises at least the lower limbs and a trunk. In the robot, a hip joint which connects the lower limbs and the trunk possesses at least a degree of freedom in correspondence with a hip joint yaw axis which is included in the hip joint. The robot further comprises an offset setting mechanism for arbitrarily offsetting the hip joint yaw axis from the hip joint in a roll axis direction.
According to a second aspect of the present invention, there is provided a leg-movement-type robot which moves using lower limbs. The robot comprises at least the lower limbs and a trunk. In the robot, a hip joint which connects the lower limbs and the trunk possesses at least a degree of freedom in correspondence with a hip joint yaw axis which is included in the hip joint. The hip joint yaw axis is offset from the hip joint in a roll axis direction.
According to a third aspect of the present invention, there is provided a leg-movement-type robot which moves using lower limbs. The robot comprises at least the lower limbs and a trunk. In the robot, a hip joint yaw axis used for changing the direction of a foot tip is offset from the location of a hip joint used for walking using the feet.
In the robots of the first to third aspects of the present invention, the amount of offset of the hip joint yaw axis from the location of the hip joint can be adjusted, so that it is possible to accommodate to the effects of the movement of the center of gravity produced in accordance with the mode of use of the robot in order to flexibly balance the weights of the upper and lower limbs. Therefore, it is possible to make the robot walk smoothly and naturally while it is in an erect posture.
By offsetting the hip joint axis, the size of the portion of the robot corresponding to the waist can be made smaller and compact, so that it is possible to form a robot whose mechanical units are dimensionally proportioned with respect to each other. In other words, it is possible to form a robot which has a proportioned external appearance close to that the natural form of the body of an animal (which walks while it is in an erect posture), such as a human being or a monkey.
When the joint yaw axis is offset from the location of the hip joint in the backward direction or in the direction opposite to the direction of movement, the location of the center of gravity of the entire robot is situated forwardly of the hip joint yaw axis. Therefore, in order to ensure stability in the pitch direction, the hip joint yaw axis is disposed behind the location of the center of each of the left and right feet. In this case, even if the hip joint yaw axis is rotated to change the direction of a foot, interference between the left and right feet can be reduced. In other words, since the width of the crutch does not need to be increased, the posture of the robot can be easily controlled in order to allow it to walk stably on two feet.
According to a fourth aspect of the present invention, there is provided a leg-movement-type robot which moves using lower limbs. The robot comprises at least the lower limbs and a trunk. In the robot, a hip joint which connects the lower limbs and the trunk possesses at least a degree of freedom in correspondence with a hip joint yaw axis which is included in the hip joint. The robot further comprises an offset setting mechanism for arbitrarily offsetting the hip joint yaw axis from the trunk in a roll axis direction.
According to a fifth aspect of the present invention, there is provided a leg-movement-type robot which moves using lower limbs. The robot comprises at least the lower limbs and a trunk. In the robot, a hip joint which connects the lower limbs and the trunk possesses at least a degree of freedom in correspondence with a hip joint yaw axis which is included in the hip joint. The hip joint yaw axis is offset from the trunk in a roll axis direction.
According to a sixth aspect of the present invention, there is provided a leg-movement-type robot which moves using lower limbs. The robot comprises at least the lower limbs and a trunk. In the robot, a hip joint yaw axis used for changing the direction of a foot tip is offset from the trunk.
According to the robots of the fourth to sixth aspects of the present invention, the amount of offset of the hip joint yaw axis from the trunk can be adjusted, so that it is possible to accommodate to the effects of the movement of the center of gravity in order to flexibly balance the weights of the upper and lower limbs. Therefore, it is possible to make the robot walk smoothly and naturally while it is in an erect posture.
The basic movement of, for example, a human being which walks on two feet is based on a forwardly tilted posture. Therefore, the robot can easily exhibit the natural movement of a human being when the trunk which corresponds to the waist of a human being is disposed towards the front. According to the robots in accordance with the fourth to the six aspects, the walking of a human being can be faithfully emulated by offsetting the hip joint yaw axis from the trunk in the roll axis direction.
By performing an offsetting operation and moving the center of gravity of the entire robot slightly forward, the robot can easily balance itself in terms of its weight while it is walking.
According to a seventh aspect of the present invention, there is provided a leg-movement-type robot which moves using lower limbs. The robot comprises at least the lower limbs and a trunk. In the robot, the trunk is offset from the lower limbs in a roll axis direction.
According to an eighth aspect of the present invention, there is provided a leg-movement-type robot which moves using lower limbs. The robot comprises upper limbs, the lower limbs, and a trunk. In the robot, the upper limbs are offset from the lower limbs in a roll axis direction.
According to a ninth aspect of the present invention, there is provided a robot of a type which spreads the legs thereof based on rotational degrees of freedom provided in correspondence with a hip joint roll axis, a hip joint pitch axis, and a hip joint yaw axis. In the robot, at least the lower limbs and a trunk are mounted substantially vertically along a body axis direction, and the hip joint yaw axis is offset from the body axis by a predetermined amount.
According to a tenth aspect of the present invention, there is provided a robot of a type which spreads the legs thereof based on rotational degrees of freedom provided in correspondence with a hip joint roll axis, a hip joint pitch axis, and a hip joint yaw axis. In the robot, at least lower limbs and a trunk are mounted substantially vertically along a body axis direction, and the hip joint yaw axis is offset from the body axis by a predetermined amount in a negative roll axis direction.
According to an eleventh aspect of the present invention, there is provided a joint device for a robot comprising a plurality of joints. In the joint device, at least rotational degrees of freedom in correspondence with a roll axis, a pitch axis, and a yaw axis are provided, and the yaw axis is offset in a roll axis direction from an axis perpendicular to the roll axis and the pitch axis.
According to a twelfth aspect of the present invention, there is provided a joint device for a robot comprising a plurality of joints. In the joint device, at least rotational degrees of freedom provided in correspondence with a roll axis, a pitch axis, and a yaw axis are provided, and the yaw axis is situated at a twisting location with respect to both the roll axis and the pitch axis.
Other objects, feature, and advantages of the present invention will be made clear from the detailed description given in conjunction with the embodiment described below and the attached drawings.